All movement produces sound waves but not all sounds can be heard with the human ear.
Did you ever notice that you cannot hear some sounds? Have you ever heard a group of neighbourhood dogs barking, and when you listen for what they are barking at, there is nothing to be heard? That is because the sound is inaudible to the human ear. If the pitch of a sound has either a very high or very low frequency, we may not be able to hear it. Dogs, dolphins and bats hear higher-frequency sounds than we can. The same vibrations that cause sound waves can sometimes be felt as well as heard. Deaf people can sense this movement to feel what their ears cannot hear.
1 & 1/2 hours, including time for aesthetic design
Present the students with a piece of sheet metal (or a sturdy piece of cardboard paper) and a piece of fabric, each of equal size and shape. Refer back to the drum activity and remind students of the various sounds the different skins made. Sometimes, it was very difficult to hear the drum noise (possibly because of the type of skin or how tightly it was secured to the drum). Keep in mind that the looser or more flexible an object, the slower it vibrates. The slower it vibrates, the lower the frequency, and the lower the pitch it will produce.
Holding the corner of the paper, wiggle it, and ask the students to determine if the sound was audible or inaudible. Next, wiggle the fabric. Be sure to wiggle them both with the same amount of force. Ask if the students can explain why one was audible and the other not. Introduce the idea of frequency and its relation to audibility. Remind students about the relationship between vibration, speed and pitch. Discuss the relationship between frequency and pitch.
Guitars can be made with a simple frame and string. Using the materials provided, construct a guitar. Be sure to make it pleasing to the eyes, as well as the ears. Once you have designed it, test it to see that all of the strings vibrate with an audible frequency.
There are a variety of stringed instruments you can introduce to the students. The harp is an example of a multi-stringed instrument. As an add-on activity, you can explore other instruments or even invent your own.
If you know someone who plays guitar or another stringed instrument, you may want to invite them to the class so they can play a tune for the students. First, have the guest tune the guitar, to demonstrate how tightening or loosening the strings affects the pitch. Ask the guitarist to demonstrate how a tuning fork or digital tuner is used to easily adjust the pitch. Have the students discuss how they imagine these tuning tools work. Ask your guest to demonstrate the different sounds made by both strumming and picking the strings. If your guest has an electric guitar, a second extension activity could lead into a lesson on electricity and its applications.
Sounds Like Science - Drums
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